Spatial, temporal and source contribution assessments of black carbon over the northern interior of South Africa

After carbon dioxide (CO2) aerosol black carbon (BC) is considered to be the second most important contributor to global warming. This paper presents equivalent black carbon (eBC) (derived from an optical absorption method) data collected from three sites in the interior of South Africa where continuous measurements were conducted, i.e. Elandsfontein, Welgegund and Marikana, as well elemental carbon (EC) (determined by evolved carbon method) data at five sites where samples were collected once a month on a filter and analysed offline, i.e. Louis Trichardt, Skukuza, Vaal Triangle, Amersfoort and Botsalano. Analyses of eBC and EC spatial mass concentration patterns across the eight sites indicate that the mass concentrations in the South African interior are in general higher than what has been reported for the developed world and that different sources are likely to influence different sites. The mean eBC or EC mass concentrations for the background sites (Welgegund, Louis Trichardt, Skukuza, Botsalano) and sites influenced by industrial activities and/or nearby settlements (Elandsfontein, Marikana, Vaal Triangle and Amersfoort) ranged between 0.7 and 1.1, and 1.3 and 1.4 ae gm 3, respectively. Similar seasonal patterns were observed at all three sites where continuous measurement data were collected (Elandsfontein, Marikana and Welgegund), with the highest eBC mass concentrations measured from June to October, indicating contributions from household combustion in the cold winter months (June-August), as well as savannah and grassland fires during the dry season (May to mid-October). Diurnal patterns of eBC at Elandsfontein, Marikana and Welgegund indicated maximum concentrations in the early mornings and late evenings, and minima during daytime. From the patterns it could be deduced that for Marikana and Welgegund, household combustion, as well as savannah and grassland fires, were the most significant sources, respectively. Possible contributing sources were explored in greater detail for Elandsfontein, with five main sources being identified as coal-fired power stations, pyrometallurgical smelters, traffic, household combustion, as well as savannah and grassland fires. Industries on the Mpumalanga Highveld are often blamed for all forms of pollution, due to the NO2 hotspot over this area that is attributed to NOx emissions from industries and vehicle emissions from the Johannesburg-Pretoria megacity. However, a comparison of source strengths indicated that household combustion as well as savannah and grassland fires were the most significant sources of eBC, par-ticularly during winter and spring months, while coal-fired power stations, pyrometallurgical smelters and traffic contribute to eBC mass concentration levels year round.Peer reviewe

Volatile organic compounds(VOC's) analysis from Cape Town haze ll study

Student Number: 9503012G Master of Science. School of Geography, Archaeology and Environmental StudiesA brown haze which builds-up over Cape Town under calm and cold weather conditions causes public concern. The brown haze is thought to be due to the gaseous and particulate emissions from the city, industries, traffic and townships in the Cape Town region. Volatile organic carbon (VOCs) compounds are an important component of the haze layer particularly because of their reactivity. VOCs play an important role in the carbon budget and radiation balance, regional oxidant balance, and in the distribution of ozone and other reactive gases, both at the regional and global scale. In this study the variation in ambient VOC concentrations during brown and non-brown haze days over Cape Town during July and August 2003 were characterised. Ambient air samples were collected in evacuated stainless steel canistes from the South African Weather Service (SAWS) research aircraft (Aerocommander, ZS-JRB) and later analysed by gas chromotography equipped with a flame ionisation detector (GC-FID). Benzene, toluene, ethylbenzene and xylene (BTEX) were the specific VOCs targeted for this study. Comparable meteorology data was also collected to determine the effects of wind field and atmospheric stability on BTEX concentrations